Journal articles on the topic 'Collapses'
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1
Hu, Wentao, and Tandong Yao. "Geometric similarity of the twin collapsed glaciers in the west Tibet." Open Geosciences 13, no. 1 (January 1, 2021): 1463–75. http://dx.doi.org/10.1515/geo-2020-0316.
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Abstract Two adjacent glaciers collapsed consecutively in the Western Xizang Autonomous Region, China, on July 17 and September 21, 2016, presumably triggered by relatively intensive climate change in this region, leading to massive downstream ice and mud avalanches. After these twin glacier collapses, there have been many researches, which mainly focus on the physical characteristics of these two glaciers while lack the differences between them and the other glaciers. In this study, the geometric features and energy distribution along the glacier centerlines are investigated to identify the differences between these two collapsed glaciers and other glaciers in the western Tibetan Plateau. The anomaly of climate change is presumed to be the trigger of the twin glacier collapses in accordance with existing research results, whereas in this study, the striking geometric similarity between the centerlines of the twin glaciers, which is quantitatively interpreted by the Fréchet distance among the glacier centerlines, unearth some novel mechanisms. The essential point in these new mechanisms is the energy distribution along the glacier centerlines. A hypothesis based on the principle of energy conservation is derived to demonstrate the mechanisms and dynamic processes of the glacier collapses. Furthermore, on the basis of the geometric similarity and energy distribution of the glacier centerlines, a risk assessment of glacier collapse in the western Tibetan Plateau is implemented to facilitate glacier disaster prevention.
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Marsudi, Dianita Ratna Kusumastuti, Nursetiaji Pamungkas, Dedi Budi Setiawan, Primasiwi Harprastanti, and Marton. "Study of Structural Analysis of Damaged Concrete Beams Strenghted with Carbon Fiber Reinforced Polymer." International Journal of Advances in Scientific Research and Engineering 08, no. 04 (2022): 29–39. http://dx.doi.org/10.31695/ijasre.2022.8.4.4.
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It is necessary to repair the cracks in the concrete structure to prevent further damage that can lead to the collapse of the structure. Repairs can restore and increase the strength of structural elements so that they are able to withstand the load in accordance with the design load, finally further decisions can be made for the next function. The results of the flexural strength test of K-150 collapsed concrete beams 100% able to withstand a load of 58 kN, K-250 collapsed 100% able to withstand a load of 64.33 kN, K-150 coated with CRFP tensile part collapsed 100% able to withstand a load of 82 kN, K -250 is coated with CRFP, the tensile part collapses 100% able to withstand a load of 91.67 kN, the quality of K-250 collapses 60% is able to withstand a load of 39.17 kN. K-250 strength concrete beam collapsed 60% maximum CRFP repair able to withstand a load of 87.67 kN. For testing of concrete beams with f'c quality of 20.71 MPa, 100% collapse with a maximum average of 29.00 MPa. The flexural strength of the concrete beam with f'c quality is 20.71 MPa, 60% collapse with an average load of 19.00 MPa. For the flexural strength of the f'c 20.71 MPa concrete beam, improvements were made to be able to withstand an average load of 52.86 MPa. Analysis of the test results by increasing the area and CRFP can increase the bearing capacity of concrete blocks. If in a construction work there is a doubt from the user about the portal being built, then CRFP can increase its flexural strength.
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Yang, Xiaoning, Brian W. Stump, and W. Scott Phillips. "Source mechanism of an explosively induced mine collapse." Bulletin of the Seismological Society of America 88, no. 3 (June 1, 1998): 843–54. http://dx.doi.org/10.1785/bssa0880030843.
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Abstract Mining explosions and collapses, in addition to earthquakes, may trigger the future Comprehensive Test Ban Treaty (CTBT) monitoring system. Many shallow, spontaneously occurring mine collapses have implosional source mechanisms that might provide a physical basis to discriminate them from explosions. In this study, an explosively induced mine collapse was investigated. The collapse occurred immediately after the support pillars of a 320-m-deep underground mine opening were destroyed by explosives. It had an Lg body-wave magnitude (mbLg) of 2.8. We analyzed free-surface ground-motion data (within 1200 m) from the collapse by waveform forward modeling and time-dependent source moment-tensor inversion. The results indicate that the source mechanism of the collapse can be represented by a horizontal opening and closing crack. The time functions of the diagonal source moment-tensor components are similar to that of a spall source accompanying an underground explosion. A unique source characteristic of the induced collapse is that, unlike spontaneous collapses, the induced collapse initiated as a tensile crack. Because of the initially expansive source characteristic, this kind of induced mine collapses may pose some difficulties to the seismic discrimination problem. Despite the similarities between the induced mine collapse and underground explosions, the collapse has a more band-limited source spectrum and seems to be more efficient in shear and surface-wave generation.
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Ramalho, Ricardo S., Gisela Winckler, José Madeira, George R. Helffrich, Ana Hipólito, Rui Quartau, Katherine Adena, and Joerg M. Schaefer. "Hazard potential of volcanic flank collapses raised by new megatsunami evidence." Science Advances 1, no. 9 (October 2015): e1500456. http://dx.doi.org/10.1126/sciadv.1500456.
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Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of triggering megatsunamis with highly catastrophic effects. Yet, evidence for the generation and impact of collapse-triggered megatsunamis and their high run-ups remains scarce or is highly controversial. Therefore, doubts remain on whether island flank failures truly generate enough volume flux to trigger giant tsunamis, leading to diverging opinions concerning the real hazard potential of such collapses. We show that one of the most prominent oceanic volcanoes on Earth—Fogo, in the Cape Verde Islands—catastrophically collapsed and triggered a megatsunami with devastating effects ~73,000 years ago. Our deductions are based on the recent discovery and cosmogenic3He dating of tsunamigenic deposits found on nearby Santiago Island, which attest to the impact of this giant tsunami and document wave run-up heights exceeding 270 m. The evidence reported here implies that Fogo’s flank failure involved at least one fast and voluminous event that led to a giant tsunami, in contrast to what has been suggested before. Our observations therefore further demonstrate that flank collapses may indeed catastrophically happen and are capable of triggering tsunamis of enormous height and energy, adding to their hazard potential.
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Ivanov, Plamen, Boyko Berov, and Nikolai Dobrev. "Mapping of the terrains to rockfall susceptibility." Engineering Geology and Hydrogeology 32, no. 1 (2018): 31–38. http://dx.doi.org/10.52321/igh.32.1.31.
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Rock collapses phenomena are one of the main processes constituting the geological hazard. Most commonly, the concept of "collapses" covers several different types of rock deformations: rockfall (linear and wedge-shaped), rock toppling, etc. It is difficult to predict the exact moment of the occurrence of a rock collapse. For this reason, it is necessary to know the potentially dangerous regions and areas in which this phenomenon may occur or to plot the sites by susceptibility to rock collapses. This will give an idea of location of hazardous areas with preconditions for collapses, and on this basis the necessary preventive measures can be identified. The main types of rock collapses and slope conditions - engineering geological, geomorphological, tectonic, are discussed. The methodological approach is given for the mapping of the terrains by susceptibility to rock collapses. Issues related to the scale of the maps compiled are clarified.
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Reznik, Рetro, Sergiy Grebenchuk, Roman Koreniev, and Vitaliy Bondarenko. "Research of the specific steel shells progressive collapse prevention." ACADEMIC JOURNAL Series: Industrial Machine Building, Civil Engineering 1, no. 52 (July 5, 2019): 58–64. http://dx.doi.org/10.26906/znp.2019.52.1676.
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The article deals with coatings in the form of the specific steel shells. After a detailed analysis certain number of accidentsand collapses, these collapses can be classified as “progressive” collapse. The main purpose of the article is the developmentof design algorithms for evaluation of the stress-strain state and preventing the progressive collapse of the specific steelshells. The method of prevention progressive collapse has been developed in the form of a constructive modernization.The comparative finite-element analysis of the strained-strain state of the specific shells original models, models of discretecontinualribbed shells (with constructive upgrading) and models of solid ribbed shells has been carried out. From the analysisresults it can be concluded that the proposed modernization method can be considered as one of the possible options forpreventing progressive collapses and increasing the bearing capacity of specific steel shells.
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Mohamadi, Bahaa, Timo Balz, and Ali Younes. "Towards a PS-InSAR Based Prediction Model for Building Collapse: Spatiotemporal Patterns of Vertical Surface Motion in Collapsed Building Areas—Case Study of Alexandria, Egypt." Remote Sensing 12, no. 20 (October 12, 2020): 3307. http://dx.doi.org/10.3390/rs12203307.
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Buildings are vulnerable to collapse incidents. We adopt a workflow to detect unusual vertical surface motions before building collapses based on PS-InSAR time series analysis and spatiotemporal data mining techniques. Sentinel-1 ascending and descending data are integrated to decompose vertical deformation in the city of Alexandria, Egypt. Collapsed building data were collected from official sources, and overlayed on PS-InSAR vertical deformation results. Time series deformation residuals are used to create a space–time cube in the ArcGIS software environment and analyzed by emerging hot spot analysis to extract spatiotemporal patterns for vertical deformation around collapsed buildings. Our results show two spatiotemporal patterns of new cold spot or new hot spot before the incidents in 66 out of 68 collapsed buildings between May 2015 and December 2018. The method was validated in detail on four collapsed buildings between January and May 2019, proving the applicability of this workflow to create a temporal vulnerability map for building collapse monitoring. This study is a step forward to create a PS-InSAR based model for building collapse prediction in the city.
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Kremer, Kyle, Claire S. Ye, Sourav Chatterjee, Carl L. Rodriguez, and Frederic A. Rasio. "The Role of “black hole burning” in the evolution of dense star clusters." Proceedings of the International Astronomical Union 14, S351 (May 2019): 357–66. http://dx.doi.org/10.1017/s1743921319007269.
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AbstractAs self-gravitating systems, dense star clusters exhibit a natural diffusion of energy from their innermost to outermost regions, leading to a slow and steady contraction of the core until it ultimately collapses under gravity. However, in spite of the natural tendency toward “core collapse,” the globular clusters (GCs) in the Milky Way exhibit a well-observed bimodal distribution in core radii separating the core-collapsed and non-core-collapsed clusters. This suggests an internal energy source is at work, delaying the onset of core collapse in many clusters. Over the past decade, a large amount of work has suggested that stellar black holes (BHs) play a dynamically-significant role in clusters throughout their entire lifetimes. Here we review our latest understanding of BH populations in GCs and demonstrate that, through their dynamical interaction with their host cluster, BHs can naturally explain the distinction between core-collapsed and non-core-collapsed clusters through a process we call “black hole burning.”
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Luo, Jing, Weilin Xu, Jun Deng, Yanwei Zhai, and Qi Zhang. "Experimental Study on the Impact Characteristics of Cavitation Bubble Collapse on a Wall." Water 10, no. 9 (September 15, 2018): 1262. http://dx.doi.org/10.3390/w10091262.
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As a hydrodynamic phenomenon, cavitation is a main concern in many industries such as water conservancy, the chemical industry and medical care. There are many studies on the generation, development and collapse of cavitation bubbles, but there are few studies on the variation of the cyclic impact strength on walls from the collapse of cavitation bubbles. In this paper, a high-speed dynamic acquisition and analysis system and a pressure measuring system are combined to study the impact of a cavitation bubble generated near a wall for various distances between the cavitation bubble and the wall. The results show that (1) with the discriminating criteria of the impact pressure borne by the wall, the critical conditions for the generation of a micro-jet in the collapse process of the cavitation bubbles are obtained, and therefore collapses of cavitation bubbles near the wall are mainly divided into primary impact area collapses, secondary impact area collapses and slow release area collapses; (2) it can be seen from the impact strength of the cavitation bubble collapse on the wall surface that the impact of cavitation bubbles on the wall surface during the first collapse decreases as γ (the dimensionless distance between the cavitation bubble and the wall) increases, but the impact of the second collapse on the wall surface increases first and then decreases sharply. When γ is less than 1.33, the impact on the wall surface is mainly from the first collapse. When γ is between 1.33 and 2.37, the impact on the wall surface is mainly from the second collapse. These conclusions have potential theoretical value for the utilization or prevention and control technologies for cavitation erosion.
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Aguilar, L. A., D. Merritt, and M. Duncan. "Cold Collapse as a Way of Making Elliptical Galaxies." Symposium - International Astronomical Union 127 (1987): 519–20. http://dx.doi.org/10.1017/s0074180900186036.
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SummaryWe investigate whether dissipationless collapse starting from very cold, non-rotating initial conditions can produce objects resembling real elliptical galaxies. We also study the effect of various initial geometries on the shape of the final object. Collapses that are initially very cold (2T/W < 0.1) are different from warmer collapses, due to the presence of a dynamical instability associated with clumping of nearly-radial orbits (Polyachenko 1981). This instability can produce very elongated bars (1.6 to 2.1 axis ratio) from spherical initial conditions. the instability is also present in models evolved from oblate and triaxial initial conditions. Warm collapses tend to preserve their initial shapes. Cold initial conditions produce objects whose surface density profiles are well fit by a de-Vaucouleurs law; warm collapses, on the other hand, produce a core-halo profile. A large collapse factor seems necessary to produce objects resembling real galaxies; the same collapse factor guarantees the presence of the radial orbit instability. It thus appears that initial flattening is not crucial for producing prolate or nearly prolate galaxies. Oblate galaxies, on the contrary, seem very difficult to form, unless extremely flattened initial conditions are invoked. Preliminary experiments suggest that these results are not changed by realistic amounts of angular momentum.
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Vincent, C., E. Thibert, M. Harter, A. Soruco, and A. Gilbert. "Volume and frequency of ice avalanches from Taconnaz hanging glacier, French Alps." Annals of Glaciology 56, no. 70 (2015): 17–25. http://dx.doi.org/10.3189/2015aog70a017.
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AbstractVery large volumes of ice break off regularly from Taconnaz hanging glacier, French Alps. During winter, when the snow mantle is unstable, these collapses can trigger very large avalanches that represent a serious threat to inhabited areas below. Photogrammetric measurements have been performed over 1 year to assess the volume and frequency of the largest collapses. Major collapses occur when the glacier reaches a critical geometry. After a major ice collapse, the glacier is in a minimal position and subsequently recharges over 6 months to reach the maximum position again. This critical geometry is a necessary but not sufficient condition for further large collapses. Large collapses do not systematically occur in the maximum position, as ice is often removed by disintegration into small ice blocks. For two major collapses, the volume of ice breaking off has been assessed at ~275 000 m3. Photogrammetric measurements were used to determine an ice flux of 820 000 m3 a–1 through the studied ice stream, in agreement with an assessment based on ice-flow modeling. This ice flux estimation was used to determine the average ice volumes breaking off over surveyed periods.
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Nte, AR, and N. Gabriel-Job. "Tetanus with multiple wedge vertebral collapses: A case report in a 13 year old girl." Nigerian Journal of Paediatrics 40, no. 2 (April 8, 2013): 189–91. http://dx.doi.org/10.4314/njp.v40i2.17.
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Data from the case records dary School Class two girl managed at the Department of Paediatrics of the University of Port Harcourt Teaching Hospital were extracted for presentation to highlight vertebral collapse as an uncommon complication of paediatric tetanus and the associated management challenges. The girl presented with complaints of back pains-11 days, inability to open her mouth- 9 days, jerking of the body- 8 days and upper back swelling-6 days following bruises from corporal punishment in her school. She was diagnosed to have tetanus with vertebral collapses of T3-T6. Tuberculosis and other causes of vertebral collapse were excluded. The tetanus was successfully treated but she left against medical advice and defaulted from follow-up for the management of the vertebral collapses. Poverty, ignorance and belief in traditional health care were major obstacles to her management.Key words: Multiple wedge vertebral collapses in tetanus
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Wang, Yan, Yong Jun Liu, and Tai Bin Wang. "A Summary Review of Progressive Collapse of Reinforced Concrete Frame Structure under Fire." Advanced Materials Research 1065-1069 (December 2014): 2315–18. http://dx.doi.org/10.4028/www.scientific.net/amr.1065-1069.2315.
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In recent years, many progressive collapse accidents have occurred at home and abroad, due to the progressive collapses of a structure that often disproportion between initial damages and large collapses, these accidents caused significant casualties and serious economic losses. This paper first analyzes the research background and the definition of progressive collapse, then contrasts China with Britain, the United States, Europe and other countries for theory research status, specification research status, engineering and simulation research status, prevention measures of progressive collapse. Compared with other countries I have found that if our country introduced a comprehensive related design specifications, some progressive collapse accidents can be avoided or ease. So there will be plenty of work to be done in our country.
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Petitgas, Pierre, Dave H. Secor, Ian McQuinn, Geir Huse, and Nancy Lo. "Stock collapses and their recovery: mechanisms that establish and maintain life-cycle closure in space and time." ICES Journal of Marine Science 67, no. 9 (June 23, 2010): 1841–48. http://dx.doi.org/10.1093/icesjms/fsq082.
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Abstract Petitgas, P., Secor, D. H., McQuinn, I., Huse, G., and Lo, N. 2010. Stock collapses and their recovery: mechanisms that establish and maintain life-cycle closure in space and time. – ICES Journal of Marine Science, 67: 1841–1848. Experience has established that the recovery of many collapsed stocks takes much longer than predicted by traditional fishery population models. We put forward the hypothesis that stock collapse is associated with disruption of the biological mechanisms that sustain life-cycle closure of intrapopulation contingents. Based on a review of case studies of nine marine fish stocks, we argue that stock collapses not only involve biomass loss, but also the loss of structural elements related to life-cycle diversity (contingents), as well as the breakdown of socially transmitted traditions (through a curtailed age range). Behavioural mechanisms associated with these structural elements could facilitate recovery of depleted populations. Migratory behaviour is argued to relate to phenotypic plasticity and the persistence of migration routes to social interactions. The case studies represent collapsed or depleted populations that recovered after a relatively short period (striped bass, capelin), after more than a decade (herring and sardine), or not at all (anchovy, cod). Contrasting the population dynamics from these stocks leads us to make a distinction between a depleted and a collapsed population, where, in addition to biomass depletion, the latter includes damage to contingent structure or space-use pattern. We also propose a mechanism to explain how lost habitats are recolonized.
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Anosike, Nwabueze Michael. "VIEWS OF CONSTRUCTION PROFESSIONALS’ ON THE CAUSES AND REMEDIES OF BUILDING COLLAPSE IN NIGERIA." International Journal of Engineering Technologies and Management Research 8, no. 6 (July 6, 2021): 68–85. http://dx.doi.org/10.29121/ijetmr.v8.i6.2021.976.
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The collapse of building has been an issue of great concern to all and sundry in Nigeria and yet these buildings are major contributors to the development of any nation. Therefore, when a building collapses, it fails to render the functions which it should perform to the people and the government. A building is regarded as collapsed if the whole structure or part thereof has fallen down and therefore cannot serve the purpose for which it was intended. When building collapses, it generates deep emotional reactions from every segment of the population constituting great losses to the country in terms of physical, human and material resources. Therefore, the aim of this research is to assess the opinion of construction professionals who are perceived as critical stakeholders on the causes as well as to proffer remedies to curb the menace. The case study is Owerri municipal council, Imo State, Nigeria. A well-structured four-point Scale questionnaire was drawn and administered to 250 selected sampled respondents to elicit data. Out of that the 250 respondents, 193 representing 77% valid respondents were retrieved and utilized in the study analysis. The analysis revealed that all critical construction stakeholders were implicated as contributors towards the incidences of building collapse. The study recommends among others that, Government, professionals’ as well as other critical stakeholders should adhere strictly to their statutory roles in order to curb the menace of building collapse in Nigeria.
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Vázquez-Semadeni, Enrique, Alejandro González-Samaniego, Manuel Zamora-Avilés, and Pedro Colín. "Cluster Assembly in Hierarchically Collapsing Clouds." Proceedings of the International Astronomical Union 12, S316 (August 2015): 196–201. http://dx.doi.org/10.1017/s174392131500914x.
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AbstractWe discuss the mechanism of cluster formation in hierarchically collapsing molecular clouds. Recent evidence, both observational and numerical, suggests that molecular clouds (MCs) may be undergoing global, hierarchical gravitational collapse. The “hierarchical” regime consists of small-scale collapses within larger-scale ones. The latter implies that the star formation rate increases systematically during the early stages of evolution, and occurs via filamentary flows onto “hubs” of higher density, mass, and velocity dispersion, and culminates a few Myr after than the small-scale collapses have started to form stars. In turn, the small-scale collapses occur in clumps embedded in the filaments, and are themselves falling into the larger potential well of the still-ongoing large-scale collapse. The stars formed in the early, small-scale collapses share the infall motion of their parent clumps towards the larger potential trough, so that the filaments feed both gaseous and stellar material to the hubs. This leads to the presence of older stars in a region where new protostars are still forming, to a scale-free or fractal structure of the clusters, in which each unit is composed of smaller-scale ones, and to the eventual merging of the subunits, explaining the observed structural features of open clusters.
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Gilbert, Adrien, Silvan Leinss, Jeffrey Kargel, Andreas Kääb, Simon Gascoin, Gregory Leonard, Etienne Berthier, Alina Karki, and Tandong Yao. "Mechanisms leading to the 2016 giant twin glacier collapses, Aru Range, Tibet." Cryosphere 12, no. 9 (September 7, 2018): 2883–900. http://dx.doi.org/10.5194/tc-12-2883-2018.
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Abstract. In north-western Tibet (34.0∘ N, 82.2∘ E) near lake Aru Co, the entire ablation areas of two glaciers (Aru-1 and Aru-2) suddenly collapsed on 17 July and 21 September 2016. The masses transformed into ice avalanches with volumes of 68 and 83×106 m3 and ran out up to 7 km in horizontal distance, killing nine people. The only similar event currently documented is the 130×106 m3 Kolka Glacier rock and ice avalanche of 2002 (Caucasus Mountains). Using climatic reanalysis, remote sensing, and three-dimensional thermo-mechanical modelling, we reconstructed the Aru glaciers' thermal regimes, thicknesses, velocities, basal shear stresses, and ice damage prior to the collapse in detail. Thereby, we highlight the potential of using emergence velocities to constrain basal friction in mountain glacier models. We show that the frictional change leading to the Aru collapses occurred in the temperate areas of the polythermal glaciers and is not related to a rapid thawing of cold-based ice. The two glaciers experienced a similar stress transfer from predominant basal drag towards predominant lateral shearing in the detachment areas and during the 5–6 years before the collapses. A high-friction patch is found under the Aru-2 glacier tongue, but not under the Aru-1 glacier. This difference led to disparate behaviour of both glaciers, making the development of the instability more visible for the Aru-1 glacier through enhanced crevassing and terminus advance over a longer period. In comparison, these signs were observable only over a few days to weeks (crevasses) or were absent (advance) for the Aru-2 glacier. Field investigations reveal that those two glaciers were underlain by soft, highly erodible, and fine-grained sedimentary lithologies. We propose that the specific bedrock lithology played a key role in the two Tibet and the Caucasus Mountains giant glacier collapses documented to date by producing low bed roughness and large amounts of till, rich in clay and silt with a low friction angle. The twin 2016 Aru collapses would thus have been driven by a failing basal substrate linked to increasing pore water pressure in the subglacial drainage system in response to increases in surface melting and rain during the 5–6 years preceding the collapse dates.
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Liu, Chien. "A theory of norm collapse." Rationality and Society 32, no. 2 (May 2020): 119–43. http://dx.doi.org/10.1177/1043463120921255.
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How a social norm emerges has been studied extensively. However, how a norm collapses has rarely been addressed in the literature. In this article, extending the theories of norm emergence by Coleman and Axelrod, I propose a theory of norm collapse. This theory specifies one micro mechanism and macro–micro–macro process through which a norm likely decays and eventually collapses. Then, as a test, I use computer simulation to simulate the process of the norm emergence and collapse. The result of the computer simulation demonstrates that the proposed theory has internal logical consistency. Finally, I conclude by discussing some implication of this research.
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Laffin, Matthew K., Charles S. Zender, Melchior van Wessem, and Sebastián Marinsek. "The role of föhn winds in eastern Antarctic Peninsula rapid ice shelf collapse." Cryosphere 16, no. 4 (April 13, 2022): 1369–81. http://dx.doi.org/10.5194/tc-16-1369-2022.
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Abstract. Ice shelf collapse reduces buttressing and enables grounded glaciers to contribute more rapidly to sea-level rise in a warming climate. The abrupt collapses of the Larsen A (1995) and B (2002) ice shelves on the Antarctic Peninsula (AP) occurred, at least for Larsen B, when long-period ocean swells damaged the calving front and the ice shelf was inundated with melt lakes that led to large-scale hydrofracture cascades. During collapse, field and satellite observations indicate föhn winds were present on both ice shelves. Here we use a regional climate model and machine learning analyses to evaluate the contributory roles of föhn winds and associated melt events prior to and during the collapses for ice shelves on the AP. Föhn winds caused about 25 % ± 3 % of the total annual melt in just 9 d on Larsen A prior to and during collapse and were present during the Larsen B collapse, which helped form extensive melt lakes. At the same time, the off-coast wind direction created by föhn winds helped melt and physically push sea ice away from the ice shelf calving fronts that allowed long-period ocean swells to reach and damage the front, which has been theorized to have ultimately triggered collapse. Collapsed ice shelves experienced enhanced surface melt driven by föhn winds over a large spatial extent and near the calving front, whereas SCAR inlet and the Larsen C ice shelves are affected less by föhn-wind-induced melt and do not experience large-scale melt ponds. These results suggest SCAR inlet and the Larsen C ice shelves may be less likely to experience rapid collapse due to föhn-driven melt so long as surface temperatures and föhn occurrence remain within historical bounds.
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Nulsen, P. E. J. "Gas and Galaxy Formation." Publications of the Astronomical Society of Australia 16, no. 1 (1999): 3–7. http://dx.doi.org/10.1071/as99003.
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AbstractThe theory of galaxy formation is reviewed briefly. From the evidence of clusters today, the primordial gas fraction was 20% or more. Thus, while the Universe is dominated by dark matter, gas plays an appreciable role in galaxy formation. Collapses of dwarf protogalaxies produce predominantly cold gas. It is argued that, in such cold collapses, the collapsed gas is largely self-gravitating. As a result, gas processes play a critical role in determining the visible structure of galaxies.
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Tan, Fei, Wufeiyu Tan, Feifei Yan, Xin Qi, Qinghua Li, and Zhikai Hong. "Model Test Analysis of Subsurface Cavity and Ground Collapse Due to Broken Pipe Leakage." Applied Sciences 12, no. 24 (December 19, 2022): 13017. http://dx.doi.org/10.3390/app122413017.
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Urban ground collapse is a common geological disaster characterized by its invisible nature, particularly in China, and results in significant socioeconomic losses and even loss of life. Underground pipeline breakage is the most common factor leading to urban ground collapses. Hence, it is essential to study how different types of pipeline breakages initiate the collapse mechanism. In this study, an indoor model test was conducted to directly observe the process of collapse due to broken pipe leakage. A broken pipe was put into a model box and tested by an experimental device. The results showed that among the different pipeline breakage types, vertical damage had the greatest influence on the degree of cavity development and ground collapse. Similarities were observed in the patterns of cavity evolution development and the extent of ground collapse as well, further revealing the significance of the cavity evolution process in predicting ground collapses.
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DAY, S. J., J. C. CARRACEDO, and H. GUILLOU. "Age and geometry of an aborted rift flank collapse: the San Andres fault system, El Hierro, Canary Islands." Geological Magazine 134, no. 4 (July 1997): 523–37. http://dx.doi.org/10.1017/s0016756897007243.
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The catastrophic slope failures and landslides that occur in the final stages of lateral collapses of volcanoes destroy much of the evidence for precursory deformation and the early stages of the collapses concerned. Aborted or incomplete collapse structures, although rare, are rich sources of information on these stages of development of catastrophic collapses. The San Andres fault system, on the volcanic island of El Hierro, is a relatively young (between about 545 and about 261–176 ka old) but inactive lateral collapse structure. It appears to represent an aborted giant landslide. It is developed along the flank of a steep-sided volcanic rift zone, and is bounded by a discrete strike-slip fault zone at the up-rift end, closest to the centre of the island. This geometry differs markedly from that of collapse structures on stratovolcanoes but bears some similarities to that of active fault systems on Hawaii. Although the fault system has undergone little erosion, cataclasites which formed close to the palaeosurface are well exposed. These cataclasites are amongst the first fault rocks to be described from volcano lateral collapse structures and include the only pseudotachylytes to have been identified in such structures to date. Their development at unusually shallow depths is attributed to large movements on the fault in a single event, the inferred aborted landslide, and a lack of pressurized pore water. The absence of pressurized fluids in the slumping block may have caused the San Andres fault system to cease moving, rather than develop into a giant volcanic landslide. The recognition that the San Andres fault system is inactive greatly reduces the estimated volcanic hazard associated with El Hierro. However, the lack of evidence for precursory deformation prior to the aborted landslide event is disturbing as it implies that giant lateral collapses can occur on steep-sided oceanic islands with little warning.
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Lusena, C., J. Goldsmith, and M. Mundhenk. "Nonapproximability Results for Partially Observable Markov Decision Processes." Journal of Artificial Intelligence Research 14 (March 1, 2001): 83–103. http://dx.doi.org/10.1613/jair.714.
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We show that for several variations of partially observable Markov decision processes, polynomial-time algorithms for finding control policies are unlikely to or simply don't have guarantees of finding policies within a constant factor or a constant summand of optimal. Here ``unlikely'' means ``unless some complexity classes collapse,'' where the collapses considered are P=NP, P=PSPACE, or P=EXP. Until or unless these collapses are shown to hold, any control-policy designer must choose between such performance guarantees and efficient computation.
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Pinsky, Malin L., and David Byler. "Fishing, fast growth and climate variability increase the risk of collapse." Proceedings of the Royal Society B: Biological Sciences 282, no. 1813 (August 22, 2015): 20151053. http://dx.doi.org/10.1098/rspb.2015.1053.
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Species around the world have suffered collapses, and a key question is why some populations are more vulnerable than others. Traditional conservation biology and evidence from terrestrial species suggest that slow-growing populations are most at risk, but interactions between climate variability and harvest dynamics may alter or even reverse this pattern. Here, we test this hypothesis globally. We use boosted regression trees to analyse the influences of harvesting, species traits and climate variability on the risk of collapse (decline below a fixed threshold) across 154 marine fish populations around the world. The most important factor explaining collapses was the magnitude of overfishing, while the duration of overfishing best explained long-term depletion. However, fast growth was the next most important risk factor. Fast-growing populations and those in variable environments were especially sensitive to overfishing, and the risk of collapse was more than tripled for fast-growing when compared with slow-growing species that experienced overfishing. We found little evidence that, in the absence of overfishing, climate variability or fast growth rates alone drove population collapse over the last six decades. Expanding efforts to rapidly adjust harvest pressure to account for climate-driven lows in productivity could help to avoid future collapses, particularly among fast-growing species.
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Ashraf, Fahmidah U., and Madeleine M. Flint. "Analysis of Peak Flow Distribution for Bridge Collapse Sites." Water 12, no. 1 (December 21, 2019): 52. http://dx.doi.org/10.3390/w12010052.
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Bridge collapse risk can be evaluated more rigorously if the hydrologic characteristics of bridge collapse sites are demystified, particularly for peak flows. In this study, forty-two bridge collapse sites were analyzed to find any trend in the peak flows. Flood frequency and other statistical analyses were used to derive peak flow distribution parameters, identify trends linked to flood magnitude and flood behavior (how extreme), quantify the return periods of peak flows, and compare different approaches of flood frequency in deriving the return periods. The results indicate that most of the bridge collapse sites exhibit heavy tail distribution and flood magnitudes that are well consistent when regressed over the drainage area. A comparison of different flood frequency analyses reveals that there is no single approach that is best generally for the dataset studied. These results indicate a commonality in flood behavior (outliers are expected, not random; heavy-tail property) for the collapse dataset studied and provides some basis for extending the findings obtained for the 42 collapsed bridges to other sites to assess the risk of future collapses.
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Thorson, James T., Trevor A. Branch, and Olaf P. Jensen. "Using model-based inference to evaluate global fisheries status from landings, location, and life history data." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 4 (April 2012): 645–55. http://dx.doi.org/10.1139/f2012-016.
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Assessing fishery collapses worldwide is hindered by the lack of biomass data for most stocks, leading to the use of landings-based proxies or the assumption that existing stock assessments are globally representative. We argue that the use of sparse assessments to evaluate fishery status requires model-based inference because assessment availability varies spatially and temporally, and we derive a model that extrapolates from assessment results to available landings, life history, and location data. This model uses logistic regression to classify stocks into different prediction bins and estimates the probability of collapse in each using cross-validation. Results show that landings, life history, and location are informative to discriminate among different probabilities of collapse. We find little evidence that regions with fewer assessments have a greater proportion of collapsed stocks, while acknowledging weak inferential support regarding regions with one or fewer assessments. Our extrapolation suggests that 4.5%–6.5% of stocks defined by landings data are collapsed, but that this proportion is increasing. Finally, we propose a research agenda that combines stock assessment and landings databases while overcoming limitations in each.
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Olatayo, Ayodeji Olusola, Olumide Afolarin Adenuga, Olajide Julius Faremi, and Aderemi M. Aderogba. "The Impact of Internal Stakeholders on Building Sustainability." ECS Transactions 107, no. 1 (April 24, 2022): 13917–35. http://dx.doi.org/10.1149/10701.13917ecst.
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Building collapses are becoming more common, resulting in the loss of lives, a waste of resources, time, and money. When a building collapses, the shock has a societal, and often even international impact, and causes disgrace to the entire chain of stakeholders in the building industry. This study identified the contributions of internal stakeholders on building collapse as well as identify the factors that influenced building collapse in Lagos State. A survey of one hundred and fifty (150) construction stakeholders was conducted with ninety-two (92) questionnaires successfully retrieved and processed for analysis. Random sampling technique was used. Data collected were analyzed using the frequency table, mean score, and ANOVA (Analysis of Variance). The result reveals that there is significant difference in the contributions of internal stakeholders on building collapse in Lagos State. The study concludes that all internal stakeholders have a significant role to play on building construction projects.
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Reznik, Petro, Mohamd Almohamad, and Vladyslav Tenesesku. "ANALYSIS OF CONSTRUCTIVE SOLUTIONS OF THE EXISTING BUILDINGS OF THE HOUSING FUND OF THE KHARKIV CITY ON THE SUBJECT OF THEIR PERFORMANCE AS A CONSEQUENCE OF THE INFLUENCE OF COMBAT ACTIONS." Collection of Scientific Works of the Ukrainian State University of Railway Transport, no. 201 (September 30, 2022): 41–56. http://dx.doi.org/10.18664/1994-7852.201.2022.267755.
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The article examines the main structural solutions of existing residential buildings inthe city of Kharkiv and analyzes their working capacity from the point of view of resistance toexplosive effects and, as a result, progressive collapse. It is known that progressive collapse ischaracteristic of extreme (emergency) cases, when due to destruction of a responsible element of thestructure as a result of a gas explosion, ammunition bursts, climatic cataclysms, transport collapses,etc a part of the building or the entire structure collapses. It is noted that every year, the interest ofthe world scientific community in the issues of progressive collapse is growing, because,unfortunately, the number of cases of avalanche-like collapse of buildings of various types isincreasing. This was facilitated by already known cases of collapses of various objects, such as theRonan Point residential building (Great Britain) in 1968 or the buildings of the World Trade Center(USA) in 2011, or the very recent case of the collapse of a residential building in Surfside (USA) in2021. At the same time, it is noted that domestic regulations do not yet specify the methodology forcalculating buildings before progressive collapse, and the existing methods of experimental andnumerical analysis still need to be refined. Unfortunately, the list of such objects is increasing, andtoday, Ukraine has added to it numerous destroyed buildings as a result of ongoing hostilities on itsterritory. Therefore, for our country in the current conditions, the issue of ensuring the future stability of all buildings, and in particular, the housing stock against progressive collapse, is an urgent issue.On the basis of the analysis of the constructive solutions of the housing development in the city ofKharkiv, the type of buildings that, according to the authors of the article, has the greatest resource,is singled out, and brief recommendations are given for its increase in the future.
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Essington, Timothy E., Pamela E. Moriarty, Halley E. Froehlich, Emma E. Hodgson, Laura E. Koehn, Kiva L. Oken, Margaret C. Siple, and Christine C. Stawitz. "Fishing amplifies forage fish population collapses." Proceedings of the National Academy of Sciences 112, no. 21 (April 6, 2015): 6648–52. http://dx.doi.org/10.1073/pnas.1422020112.
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Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches.
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Meier, Arne. "Incremental FPT Delay." Algorithms 13, no. 5 (May 15, 2020): 122. http://dx.doi.org/10.3390/a13050122.
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In this paper, we study the relationship of parameterized enumeration complexity classes defined by Creignou et al. (MFCS 2013). Specifically, we introduce two hierarchies (IncFPTa and CapIncFPTa) of enumeration complexity classes for incremental fpt-time in terms of exponent slices and show how they interleave. Furthermore, we define several parameterized function classes and, in particular, introduce the parameterized counterpart of the class of nondeterministic multivalued functions with values that are polynomially verifiable and guaranteed to exist, TFNP, known from Megiddo and Papadimitriou (TCS 1991). We show that this class TF(para-NP), the restriction of the function variant of NP to total functions, collapsing to F(FPT), the function variant of FPT, is equivalent to the result that OutputFPT coincides with IncFPT. In addition, these collapses are shown to be equivalent to TFNP = FP, and also equivalent to P equals NP intersected with coNP. Finally, we show that these two collapses are equivalent to the collapse of IncP and OutputP in the classical setting. These results are the first direct connections of collapses in parameterized enumeration complexity to collapses in classical enumeration complexity, parameterized function complexity, classical function complexity, and computational complexity theory.
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Sguotti, Camilla, Saskia A. Otto, Romain Frelat, Tom J. Langbehn, Marie Plambech Ryberg, Martin Lindegren, Joël M. Durant, Nils Chr. Stenseth, and Christian Möllmann. "Catastrophic dynamics limit Atlantic cod recovery." Proceedings of the Royal Society B: Biological Sciences 286, no. 1898 (March 13, 2019): 20182877. http://dx.doi.org/10.1098/rspb.2018.2877.
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Collapses and regime changes are pervasive in complex systems (such as marine ecosystems) governed by multiple stressors. The demise of Atlantic cod ( Gadus morhua ) stocks constitutes a text book example of the consequences of overexploiting marine living resources, yet the drivers of these nearly synchronous collapses are still debated. Moreover, it is still unclear why rebuilding of collapsed fish stocks such as cod is often slow or absent. Here, we apply the stochastic cusp model, based on catastrophe theory, and show that collapse and recovery of cod stocks are potentially driven by the specific interaction between exploitation pressure and environmental drivers. Our statistical modelling study demonstrates that for most of the cod stocks, ocean warming could induce a nonlinear discontinuous relationship between fishing pressure and stock size, which would explain hysteresis in their response to reduced exploitation pressure. Our study suggests further that a continuing increase in ocean temperatures will probably limit productivity and hence future fishing opportunities for most cod stocks of the Atlantic Ocean. Moreover, our study contributes to the ongoing discussion on the importance of climate and fishing effects on commercially exploited fish stocks, highlighting the importance of considering discontinuous dynamics in holistic ecosystem-based management approaches, particularly under climate change.
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Tian, Xia, Kaipeng Ma, Guangyu Ji, Junzhi Cui, Yi Liao, and Meizhen Xiang. "Anisotropic shock responses of nanoporous Al by molecular dynamics simulations." PLOS ONE 16, no. 3 (March 17, 2021): e0247172. http://dx.doi.org/10.1371/journal.pone.0247172.
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Mechanical responses of nanoporous aluminum samples under shock in different crystallographic orientations (<100>, <111>, <110>, <112> and <130>) are investigated by molecular dynamics simulations. The shape evolution of void during collapse is found to have no relationship with the shock orientation. Void collapse rate and dislocation activities at the void surface are found to strongly dependent on the shock orientation. For a relatively weaker shock, void collapses fastest when shocked along the <100> orientation; while for a relatively stronger shock, void collapses fastest in the <110> orientation. The dislocation nucleation position is strongly depended on the impacting crystallographic orientation. A theory based on resolved shear stress is used to explain which slip planes the earliest-appearing dislocations prefer to nucleate on under different shock orientations.
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EROFEEV, V. I. "Impossibility of Zakharov's short-wavelength modulational instability in plasmas with intense Langmuir turbulence." Journal of Plasma Physics 68, no. 1 (July 2002): 1–25. http://dx.doi.org/10.1017/s002237780200185x.
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An analysis of two experimental observations of Langmuir wave collapse is performed. The corresponding experimental data are shown as evidence against the occurrence of collapses. The physical reason preventing the collapses is found to be the nonresonant electron diffusion in momentum. In this process, plasma thermal electrons are efficiently heated at the expense of wave energy, therefore intense collisionless wave dissipation takes place. The basic reason for the underestimation of nonresonant electron diffusion in the traditional theory is shown to be the substitution of a real plasma by a plasma probabilistic ensemble.A study of nonresonant electron diffusion refraining from ensemble substitution is performed. It is shown that its intensity is sufficient for suppression of Zakharov's short-wavelength modulational plasma instability [Zakharov, V. E., Sov. Phys. JETP35, 908 (1972)]. This explains the nonoccurrence of Zakharov's Langmuir wave collapse in experiments.
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GRIFFIN, DAVID D., THOMAS D. CONLEY, and J. DAVID TALLEY. "The Bridge Collapses!" Journal of Interventional Cardiology 10, no. 3 (June 1997): 241–42. http://dx.doi.org/10.1111/j.1540-8183.1997.tb00037.x.
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Vermeulen, Freek. "When management collapses." Business Strategy Review 20, no. 2 (June 2009): 42–44. http://dx.doi.org/10.1111/j.1467-8616.2009.00597.x.
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Kadin, Jim. "The Polynomial Time Hierarchy Collapses If the Boolean Hierarchy Collapses." SIAM Journal on Computing 17, no. 6 (December 1988): 1263–82. http://dx.doi.org/10.1137/0217080.
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PIOT, B. A., D. K. MAUDE, Z. R. WASILEWSKI, K. J. FRIEDLAND, R. HEY, K. H. PLOOG, L. EAVES, M. HENINI, R. AIREY, and G. HILL. "FURTHER EVIDENCE FOR A COLLAPSE OF THE EXCHANGE-ENHANCED SPIN SPLITTING IN TWO DIMENSIONAL SYSTEMS." International Journal of Modern Physics B 18, no. 27n29 (November 30, 2004): 3597–602. http://dx.doi.org/10.1142/s0217979204027098.
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The collapse of spin splitting in the integer quantum Hall effect is investigated for a series of Al x Ga 1-x As / GaAs heterojunctions and quantum wells. Magnetoresistance measurements are performed at mK temperature, and a simple model is developed to simulate spin splitting. As expected a single-electron picture cannot reproduce the observed spin splitting, whereas a phenomenological enhanced-spin gap taking into account exchange interactions between electrons provides a good description. The phenomenological spin gap, which is linear in B at high magnetic field, collapses when the spin splitting collapses. This is consistent with previously proposed disorder-driven destruction of exchange interactions with decreasing magnetic field.
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Siddiq, Jibril Abubakar, and Professor Li Xianyi. "Challenges under Collapse of Building in Nigeria and Way to Improve It." International Journal for Research in Applied Science and Engineering Technology 10, no. 5 (May 31, 2022): 213–19. http://dx.doi.org/10.22214/ijraset.2022.42021.
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Abstract: Building collapse in Nigeria is alarming and indeed has become a subject of great concern. For the past 10 years an overwhelming number of buildings have collapsed in Nigerian rural and urban cities, with about 77% rise from the previous decade. The incidence of building failures and collapses has become major issues of concern in the development of Nigeria as the losses in terms of lives and properties are now becoming very alarming. This study provides critical reasoning and contributions regarding structural failures observed in Nigeria. To address this problem, The study aimed at exploring major causes of building collapse in Nigeria with a view of establishing effective way of solving the problem. The primary data that will be used if from the Questionnaires and field observations while secondary data will be obtained from textbooks, newspapers and Journal articles . This significant of this paper is to use building information modeling BIM to improve full project visualization, reduced construction collapse, cost, increased productivity, safer construction, better building and information analysis. Keywords: Building Information Modelling, construction, industry, management project.
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Moede, John D. "Medical Aspects of Urban Heavy Rescue." Prehospital and Disaster Medicine 6, no. 3 (September 1991): 341–48. http://dx.doi.org/10.1017/s1049023x00038784.
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The concept of Urban Heavy Rescue is gaining increasing recognition within the emergency response community. Urban Heavy Rescue has come to denote the unique demands for special equipment and personnel as the result of structural collapse. Recent earthquakes in California, the Philippines, and Soviet Armenia as well as the building collapses in Brownsville, Texas, and New York City provided excellent demonstrations of the concept of specialized structural collapse teams. These events even have prompted the Federal Emergency Management Agency (FEMA) to establish a National Urban Search and Rescue System of special task forces trained in victim location and extrication from collapsed structures. This system will comprise an immediate federal response mechanism for assisting first responders in such activities. The National Search and Rescue System was based on post-event evaluations that pointed out a need not only for more applicable equipment and trained personnel, but also for the timely placement of the these resources.
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Lei, Yanbin, Tandong Yao, Lide Tian, Yongwei Sheng, Jingjuan Liao, Huabiao Zhao, Wei Yang, et al. "Response of downstream lakes to Aru glacier collapses on the western Tibetan Plateau." Cryosphere 15, no. 1 (January 14, 2021): 199–214. http://dx.doi.org/10.5194/tc-15-199-2021.
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Abstract. The lower parts of two glaciers in the Aru range on the western Tibetan Plateau (TP) collapsed on 17 July and 21 September 2016, respectively, causing fatal damage to local people and their livestock. The giant ice avalanches, with a total volume of 150 × 106 m3, had almost melted by September 2019 (about 30 % of the second ice avalanche remained). The impact of these extreme disasters on downstream lakes has not been investigated yet. Based on in situ observation, bathymetry survey and satellite data, we explore the impact of the ice avalanches on the two downstream lakes (i.e., Aru Co and Memar Co) in terms of lake morphology, water level and water temperature in the subsequent 4 years (2016–2019). After the first glacier collapse, the ice avalanche slid into Aru Co along with a large amount of debris, which generated great impact waves in Aru Co and significantly modified the lake's shoreline and underwater topography. An ice volume of at least 7.1 × 106 m3 was discharged into Aru Co, spread over the lake surface and considerably lowered its surface temperature by 2–4 ∘C in the first 2 weeks after the first glacier collapse. Due to the large amount of meltwater input, Memar Co exhibited more rapid expansion after the glacier collapses (2016–2019) than before (2003–2014), in particular during the warm season. The melting of ice avalanches was found to contribute to about 23 % of the increase in lake storage between 2016 and 2019. Our results indicate that the Aru glacier collapses had both short-term and long-term impacts on the downstream lakes and provide a baseline in understanding the future lake response to glacier melting on the TP under a warming climate.
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bin Pokaad, Alif Zulfakar, Md Radzai bin Said, Fauzi bin Ahmad, and Mohd Nazeri bin Kamaruddin. "An Experimental on Honeycomb Core in the Axial Direction under the Quasi-Static Loading." Applied Mechanics and Materials 699 (November 2014): 405–10. http://dx.doi.org/10.4028/www.scientific.net/amm.699.405.
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This paper focuses on the quasi-static response of the aluminum honeycomb core based on an experimental work. The load-compression and energy absorb characteristics of the out-of-plane aluminium honeycomb core are studied for three varieties of the core cell sizes which are 0.01905, 0.0127 and 0.00635 m. The crushing tests were conducted on the Instron machine with a displacement control of 5 mm/min. The initial part in the load-displacement graph shows linear elastic characteristic, followed by a non-linear elastic-plastic regime before it collapses. Based on the observation, the cell sized 0.01905 m shows the global buckling collapse, but the cell sized 0.0127 and 0.00635 m collapse as progressive buckling mode. The cell size 0.00635 m shows highest energy absorption due to it has the highest density and it collapses like the progressive buckling mode compared with the others specimen.
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Ferguson-Cradler, Gregory. "Fisheries’ collapse and the making of a global event, 1950s–1970s." Journal of Global History 13, no. 3 (October 31, 2018): 399–424. http://dx.doi.org/10.1017/s1740022818000219.
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AbstractThis article analyses three fisheries crises in the post-war world – the Far East Asian Kamchatka salmon in the late 1950s, the north Atlantic Atlanto-Scandian herring of the late 1960s, and the Peruvian anchoveta of the early 1970s – to understand how each instance came to be understood as a ‘collapse’ in widely differing contexts and institutional settings, and how these crises led to changes in practices of natural resource administration and in politico-economic structures of the fishing industry. Fishery collapses were broadly understood as state failures and, in response, individual states increasingly claimed sovereignty over fish stocks and the responsibility to administer their exploitation. Collapses thus became events critical in the remaking of management regimes. Furthermore, the concept of a fisheries collapse was reconfigured in the 1970s into a global issue, representing the possible future threat of depletion of the oceans on a planetary scale.
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Papyan, Vardan, X. Y. Han, and David L. Donoho. "Prevalence of neural collapse during the terminal phase of deep learning training." Proceedings of the National Academy of Sciences 117, no. 40 (September 21, 2020): 24652–63. http://dx.doi.org/10.1073/pnas.2015509117.
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Modern practice for training classification deepnets involves a terminal phase of training (TPT), which begins at the epoch where training error first vanishes. During TPT, the training error stays effectively zero, while training loss is pushed toward zero. Direct measurements of TPT, for three prototypical deepnet architectures and across seven canonical classification datasets, expose a pervasive inductive bias we call neural collapse (NC), involving four deeply interconnected phenomena. (NC1) Cross-example within-class variability of last-layer training activations collapses to zero, as the individual activations themselves collapse to their class means. (NC2) The class means collapse to the vertices of a simplex equiangular tight frame (ETF). (NC3) Up to rescaling, the last-layer classifiers collapse to the class means or in other words, to the simplex ETF (i.e., to a self-dual configuration). (NC4) For a given activation, the classifier’s decision collapses to simply choosing whichever class has the closest train class mean (i.e., the nearest class center [NCC] decision rule). The symmetric and very simple geometry induced by the TPT confers important benefits, including better generalization performance, better robustness, and better interpretability.
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Lobkina, Valentina. "Analysis of Roof Collapse Cases Caused by Snow Loads in Russia (2001–2021)." Sustainability 13, no. 24 (December 8, 2021): 13580. http://dx.doi.org/10.3390/su132413580.
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Cases of building decay and structural damage caused by the impact of snow loads are registered every year throughout the world. Such destruction not only results in property loss, but also leads to human losses. A database on 266 cases of roof collapse caused by snow loads in Russia for the period from 2001 to 2021 was collated for this study. The data were analyzed by date and place of collapse, building data, and number of victims. The analysis showed that civilian buildings are the most vulnerable, comprising 78% of the total number of collapses, followed by industrial buildings with 15% and agricultural buildings with only 7%. The relationships between roof shape, roofing material, number of floors, and type of collapsed building were determined. The data processing results showed that low-rise residential buildings (one to two floors) with a gable roof covered with fiber cement should be considered the most vulnerable. A linear relationship was revealed between a collapse area of more than 150 m2 and the cumulative number of collapse cases. The obtained results have practical application for rating building vulnerability to natural hazards and assessing the risk of emergencies associated with snow loads.
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Ehrlich, Paul R., and Anne H. Ehrlich. "Can a collapse of global civilization be avoided?" Proceedings of the Royal Society B: Biological Sciences 280, no. 1754 (March 7, 2013): 20122845. http://dx.doi.org/10.1098/rspb.2012.2845.
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Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity.
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Allen, Brandon E., Ella Bowles, Matthew R. J. Morris, and Sean M. Rogers. "Loss of SNP genetic diversity following population collapse in a recreational walleye (Sander vitreus) fishery." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 10 (October 2018): 1644–51. http://dx.doi.org/10.1139/cjfas-2017-0164.
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Walleye (Sander vitreus) are in demand as a commercially and recreationally harvested freshwater fish in Canada. Managed populations may exhibit different phenotypic and genetic signatures from their natural counterparts. In Alberta, Canada, this fishery is recovering from population collapses attributed to intensive recreational angling. We hypothesized that historical population collapses would be associated with signatures of reduced genetic diversity. To address this question, we sampled six walleye lakes in northern Alberta, including historical tissue samples for one population, and used genotyping-by-sequencing to characterize 1081 single nucleotide polymorphisms (SNPs). Lakes were identified as unique genetic clusters except for two lakes that unexpectedly exhibited signs of genetic clustering. Using historical DNA samples, 428 homologous SNPs characterized in walleye between pre- and postpopulation collapse exhibited significant reductions in multiple estimates of genetic diversity. Collectively, our results illustrate that genotype-by-sequencing methods that integrate historical and contemporary samples in association with managed populations provide insight into the consequences of harvest pressure causing collapse.
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Yong, Kang. "Mechanical Test on Pipe Collapse under External Pressure." Advanced Materials Research 291-294 (July 2011): 1255–58. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1255.
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Many factors result in pipe collapses under certain external pressure. The relations among them have been studied by the pipe collapse tests. This pepper focused on the test analyses of steel pipe collapse resistance. Those include a pipe collapse pressure test under external pressure and illustrate both test and preparing theoretical analysis, and results of the collapse pressure with the effects on the tendency of ovality. In addition to various pipe collapse data and mechanical test methods, this study will offer a summary of the findings for the further intention of theories researches.
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Kadin, Jim. "Erratum: The Polynomial Time Hierarchy Collapses If the Boolean Hierarchy Collapses." SIAM Journal on Computing 20, no. 2 (April 1991): 404. http://dx.doi.org/10.1137/0220025.
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Gajic, Aleksandar. "Jared Diamond and Peter Turchin: Two contemporary theories of social collapse." Zbornik Matice srpske za drustvene nauke, no. 146 (2014): 85–104. http://dx.doi.org/10.2298/zmsdn1446085g.
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Theories of social collapse are not only the views that characterize ?societies deep in crisis?, but rather an expression of lack of belief in prosperity and central importance of the civilization in which we live. These theories follow processes of degradation of human societies, the decline of civilization`s powers and the loss of its cultural values resulting in their complete disappearance. This paper defines the subject of study and provides an overview of the history of these theories and their contemporary types by taking the main causes of collapse criteria as the basis for theory building. After the review of contemporary multi-factor analysis of collapse, mainly within the science of complex systems, full attention is focused on two atypical, yet very productive, contemporary theories of social collapse that are elaborated in detail: Jared Diamond`s theory, which studies social collapses by observing relations of other variables that can lead to collapse with environmental problems as central; and Peter Turchin`s theory which, revitalizing with modern scientific achievements Ibn Khaldun`s classical theory of ?asabia? (group feeling, spirit of community), sees social collapses as a consequence of the decline of cohesion provided by asabia. The final part of the work gives a critical review of these two theories and their relation with classical theories of social collapse (primarily those of Arnold Toynbee) and points to their mutual productive complementarity.
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GONZALEZ-AVILA, SILVESTRE ROBERTO, EVERT KLASEBOER, BOO CHEONG KHOO, and CLAUS-DIETER OHL. "Cavitation bubble dynamics in a liquid gap of variable height." Journal of Fluid Mechanics 682 (June 21, 2011): 241–60. http://dx.doi.org/10.1017/jfm.2011.212.
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We report on an experimental study of cavitation bubble dynamics within sub-millimetre-sized narrow gaps. The gap height is varied, while the position of the cavitation event is fixed with respect to the lower gap wall. Four different sizes of laser-induced cavitation bubbles are studied using high-speed photography of up to 430,000 frames per second. We find a strong influence of the gap height, H, on the bubble dynamics, in particular on the collapse scenario. Also, similar bubble dynamics was found for the same non-dimensional gap height η = H/Rx, where Rx is the maximum radius in the horizontal direction. Three scenarios are observed: neutral collapse at the gap centre, collapse onto the lower wall and collapse onto the upper wall. For intermediate gap height the bubble obtains a conical shape 1.4 < η < 7.0. For large distances, η > 7.0, the bubble no longer feels the presence of the upper wall and collapses hemispherically. The collapse time increases with respect to the expansion time for decreasing values of η. Due to the small scales involved, the final stage of the bubble collapse could not be resolved temporally and numerical simulations were performed to elucidate the details of the flow. The simulations demonstrate high-speed jetting towards the upper and lower walls and complex bubble splitting for neutral collapses.